Cadmium-113 NMR studies on homoleptic complexes containing thioether ligands: the crystal structures of [Cd([12]aneS4)2](ClO4)2, [Cd([18]aneS4N2)](PF6)2 and [Cd([9]aneS3)2](PF6)2

Abstract

We report the measurement of 113Cd NMR chemical shift data for homoleptic thioether and related aza and mixed aza/thiacrown complexes. In a series of Cd(II) complexes containing trithioether to hexathioether ligands, we observe solution 113Cd NMR chemical shifts in the range of 225 to 731 ppm. Upfield chemical shifts in these NMR spectra are seen whenever: (a) the number of thioether sulfur donors in the complex is decreased, (b) a thioether sulfur donor is replaced by a secondary nitrogen donor, or (c) the size of the macrocycle ring increases without a change in the nature or number of the donor atoms. Changes in the identity of non-coordinating anions such as perchlorate or hexafluorophosphate have little effect upon the 113Cd NMR chemical shift in solution. We report the X-ray structure of the complex [Cd([12]aneS4)2](ClO4)2 ([12]aneS4 = 1,4,7,10-tetrathiacyclododecane) (1) which shows the first example of octakis(thioether) coordination of a metal ion, forming an unusual eight-coordinate square antiprismatic structure. We report the X-ray structure of the complex [Cd([9]aneS3)2](PF6)2 ([9]aneS3 = 1,4,7-trithiacyclononane) (3a) which shows hexakis(thioether) coordination to form a distorted octahedral structure. We have also prepared and characterized the Cd(II) complex of a mixed azathiacrown, [Cd([18]aneS4N2)](PF6)2 ([18]aneS4N2 = 1,4,10,13-tetrathia-7,16-diazacyclooctadecane) (6). Its X-ray structure shows a distorted octahedral S4N2 environment around the Cd(II) with the ligand coordinated in the rac fashion. We observe a solvent- and temperature-dependent 14N-1H coupling in the 1H NMR spectrum of the complex which is not present in analogous complexes with this ligand.

Complexation of Cd(SeCN)2with imidazolidine-2-thione and its derivatives: Solid state, solution NMR and anti-bacterial studies

“…In the CN region of the 13 C NMR spectrum, a sharp singlet was observed at 118.54 ppm for Cd(SeCN) 2 complex and less than 1 ppm shift was observed for all [>C=S-Cd-(Se 13 CN) 2 ] complexes. This is probably due to the three bonds difference between the cadmium(II) and the 13 CN group.…”

“…This is probably due to the three bonds difference between the cadmium(II) and the 13 CN group. Therefore, the chemical shift difference between the free and bound complexes are less than one ppm.…”

“…Table 4, along with the span, Ω, which describes the breadth of the chemical shift tensor and skew, κ, describing the shape of the powder pattern. The thione 13 C isotropic shift in the complexes moves to lower frequency by about 4-5 ppm upon complexation, compared to free ligand. This also confirms that the thione form is retained in the complex in the solid state.…”

“…Natural abundance 113 Cd, 13 C and 77 Se solid state NMR spectra were obtained on a JEOL LAMBDA 500 spectrometer operating at 110.85, 125.65 and 95.35 MHz respectively, corresponding to a magnetic field of 11.74 T, at ambient temperature of 25 • C. Samples were packed into 6 mm zirconia rotors. Cross polarization and high power decoupling were employed.…”

“…The same Cd(NO 3 ) 2 · 4H 2 O sample was used to set up the Hartmann-Hahn condition for the CPMAS experiments. 13 C chemical shifts were referenced to TMS by setting the high frequency isotropic peak of solid adamantane to 38.48 ppm. The selenium chemical shifts were referenced using the secondary reference (NH 4 ) 2 SeO 4 , by setting the 77 Se peak to +1040.2 ppm relative to (CH 3 ) 2 Se [23].…”